Abstract : The kinetic equation valid for a gas with short range forces in an externally applied field is derived from the Liouville equation. The correction to the Boltzmann equation linear in eta T (the ratio of the time required for two particles to reach their asymptotic momentum inA TWO BODY COLLISION TO THE TIME REQUIRED FOR THE FIELD TO BRING A PARTICLE FROM REST TO THERMAL SPEED) is calculated. This correction is shown to vanish identically in the weak coupling limit. (Author)